First sample images of architecture and landscape have been disappointing in terms of sharpness and resolution.
Recordings of CD racks from about 1.5 meters from the tripod showed unmotivated blurred, partly in the center, partly on the edge.
So I needed a real test. The test chart placed with Siemens stars, camera with lens on the tripod oriented plan, test series with ISO 160 at 12, 14, 18, 25, 28 and 32 mm focal length and aperture settings open, customized dimmed with 1 stop and 2 aperture.
Conclusion on RAW image quality and developing with Lightroom 5.5:
This lens delivers such poor optical quality, as I with my Panasonic Lumix G 6 - have not yet experienced lenses and 2 foreign lenses (Olympus and Walimex) in the Micro Four Thirds System:
Focal Length 12mm: sharpness and resolution in the center and edge well. Extremely strong, barrel distortion.
Focal Length 14 - 28mm: sharpness and resolution in the middle of very bad against the edges a little better, but there is not really satisfactory (!?!). Distortion from approximately 18mm negligible.
Focal Length 32mm: sharpness and resolution better, of "good" but far away.
In general: The weakest area is the upper left corner.
Whether only this lens has these weaknesses ("product diversification"), or all can, and I will no longer fathom after this test. I sent it of course the next day again at Amazon.com back.
This I tested lens deserves for the optical quality unfortunately only 2 stars.
At the address of Panasonic (and unfortunately many other manufacturers): With such a lousy optical quality can be a reputation as an innovative lens manufacturer ruin very quickly. Whether that's worth the savings of no longer carried out final checks, I doubt it.
VAK